/*
 * jETeL/CloverETL - Java based ETL application framework.
 * Copyright (c) Javlin, a.s. (info@cloveretl.com)
 *  
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package org.jetel.util;

import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;

/**
 * This {@link Enumeration} implementation allows to concatenate several {@link Enumeration}s.
 * 
 * @author martin (info@cloveretl.com) (c) Javlin, a.s. (www.cloveretl.com)
 * 
 * @created 25. 11. 2016
 */
public class CompoundEnumeration<E> implements Enumeration<E> {

	private Iterator<Enumeration<E>> enumerations;

	private Enumeration<E> currentEnumeration;

	public CompoundEnumeration(List<Enumeration<E>> enumerations) {
		this.enumerations = enumerations.iterator();

		moveToNextEnumeration();
	}

	private void moveToNextEnumeration() {
		if (this.enumerations.hasNext()) {
			currentEnumeration = this.enumerations.next();
		} else {
			currentEnumeration = null;
		}
	}

	@Override
	public boolean hasMoreElements() {
		while (currentEnumeration != null) {
			if (currentEnumeration.hasMoreElements()) {
				return true;
			} else {
				moveToNextEnumeration();
			}
		}
		return false;
	}

	@Override
	public E nextElement() {
		if (!hasMoreElements()) {
			throw new NoSuchElementException();
		}
		return currentEnumeration.nextElement();
	}

}